﻿ #pragma once
#include<assert.h>
template<class K, class V>
struct AVLTreeNode
{
	// 需要parent指针，后续更新平衡因⼦可以看到
	pair<K, V> _kv;
	AVLTreeNode<K, V>* _left;
	AVLTreeNode<K, V>* _right;
	AVLTreeNode<K, V>* _parent;
	int _bf; // balance factor
	AVLTreeNode(const pair<K, V>& kv)
		:_kv(kv)
		, _left(nullptr)
		, _right(nullptr)
		, _parent(nullptr)
		, _bf(0)
	{
	}
};


template<class K, class V>
class AVLTree {
	typedef AVLTreeNode<K, V> Node;
public:
	bool IsBalanceTree() {
		return _IsBalanceTree(_root);
	}
	bool Insert(const pair<K, V>& kv) {
		if (_root == nullptr) {
			_root = new Node(kv);
			return true;
		}
		Node* cur = _root;
		Node* parent = nullptr;
		while (cur) {
			if (cur->_kv.first < kv.first) {
				parent = cur;
				cur = cur->_right;
			}
			else if (cur->_kv.first > kv.first) {
				parent = cur;
				cur = cur->_left;
			}
			else {
				return false;
			}
		}
		cur = new Node(kv);
		cur->_bf = 0;
		if (parent->_kv.first < kv.first) {
			parent->_right = cur;
		}
		else if (parent->_kv.first > kv.first) {
			parent->_left = cur;
		}
		cur->_parent = parent;

		while (parent) {
			if (cur == parent->_right) {
				parent->_bf++;
			}
			else {
				parent->_bf--;
			}

			if (parent->_bf == 0) {
				break;
			}
			else if (parent->_bf == 1 || parent->_bf == -1) {
				cur = parent;
				parent = parent->_parent;
			}
			else if (parent->_bf == 2 || parent->_bf == -2) {
				//旋转
				if (parent->_bf == -2 && cur->_bf == -1) {
					//右单旋
					RotateR(parent);
				}
				else if (parent->_bf == 2 && cur->_bf == 1) {
					//左单旋
					RotateL(parent);
				}
				else if (parent->_bf == -2 && cur->_bf == 1) {
					RotateLR(parent);
				}
				else if (parent->_bf == 2 && cur->_bf == -1) {
					RotateRL(parent);
				}
				break;
			}
			else {
				assert(false);
			}
		}
		return true;
	}
	void InOrder() {
		_InOrder(_root);
	}
private:
	int _Height(Node* root)
	{
		if (root == nullptr)
			return 0;
		int leftHeight = _Height(root->_left);
		int rightHeight = _Height(root->_right);
		return leftHeight > rightHeight ? leftHeight + 1 : rightHeight + 1;
	}
	bool _IsBalanceTree(Node* root) {
		if (root == nullptr)return true;
		int lefth = _Height(root->_left);
		int righth = _Height(root->_right);
		int bf = righth - lefth;
		if (abs(bf) >= 2 || bf != root->_bf) {
			cout << root->_kv.first << "平衡因子有问题" << endl;
			return false;
		}
		return _IsBalanceTree(root->_left) && _IsBalanceTree(root->_right);
	}
	void _InOrder(Node* root) {
		if (root == nullptr) {
			return;
		}
		_InOrder(root->_left);
		cout << root->_kv.first << ":" << root->_kv.second <<endl;
		_InOrder(root->_right);
	}
	void RotateR(Node* parent) {
		Node* subL = parent->_left;
		Node* subLR = subL->_right;

		parent->_left = subLR;
		if (subLR)
			subLR->_parent = parent;

		Node* parentP = parent->_parent;

		subL->_right = parent;
		parent->_parent = subL;

		if (parent == _root) {
			_root = subL;
			subL->_parent = nullptr;
		}
		else {
			subL->_parent = parentP;

			if (parentP->_left == parent) {
				parentP->_left = subL;
			}
			else {
				parentP->_right = subL;
			}
		}
		parent->_bf = 0;
		subL->_bf = 0;
	}

	void RotateL(Node* parent) {
		Node* subR = parent->_right;
		Node* subRL = subR->_left;

		parent->_right = subRL;
		if (subRL)
			subRL->_parent = parent;

		Node* parentP = parent->_parent;

		subR->_left = parent;
		parent->_parent = subR;

		if (parent == _root) {
			_root = subR;
			subR->_parent = nullptr;
		}
		else {
			subR->_parent = parentP;

			if (parentP->_left == parent) {
				parentP->_left = subR;
			}
			else {
				parentP->_right = subR;
			}
		}
		parent->_bf = 0;
		subR->_bf = 0;
	}
	void RotateLR(Node* parent) {
		Node* subL = parent->_left;
		Node* subLR = subL->_right;
		int bf = subLR->_bf;
		RotateL(subL);
		RotateR(parent);
		if (bf == 0) {
			subL->_bf = 0;
			parent->_bf = 0;
			subLR->_bf = 0;
		}
		else if (bf == 1) {
			subL->_bf = -1;
			parent->_bf = 0;
			subLR->_bf = 0;
		}
		else if (bf == -1) {
			subL->_bf = 0;
			parent->_bf = 1;
			subLR->_bf = 0;
		}
		else {
			assert(false);
		}
	}
	void RotateRL(Node* parent)
	{
		Node* subR = parent->_right;
		Node* subRL = subR->_left;
		int bf = subRL->_bf;
		RotateR(parent->_right);
		RotateL(parent);
		if (bf == 0)
		{
			subR->_bf = 0;
			subRL->_bf = 0;
			parent->_bf = 0;
		}
		else if (bf == 1)
		{
			subR->_bf = 0;
			subRL->_bf = 0;
			parent->_bf = -1;
		}
		else if (bf == -1)
		{
			subR->_bf = 1;
			subRL->_bf = 0;
			parent->_bf = 0;
		}
		else
		{
			assert(false);
		}
	}
private:
	Node* _root=nullptr;

};